Advanced Operating Systems

This is the home page for the "Advanced OS" course. Here, you will find (in a badly-organised form) all the material, slides, and information needed to attend the course

For the previous editions of the course, check the old websites (2018 and 2019).

Lessons:

• First lesson: 2021/04/06, 14:00 -> 16:30 (videos of the first part and second part of the lesson, in italian)
  • Introduction to the course
  • Introduction to real-time operating systems
• Second lesson: 2021/04/13, 9:30 -> 12:00 (videos of the first part and second part of the lesson, in italian)
  • Discussion about the kernel latency and how to reduce it
• Third lesson: 2021/04/20, 9:30 -> 12:00 (videos of the first part and second part of the lesson, in italian)
  • Real-Time kernels, again
  • Real-Time in user space (using PI instead of HLP for protecting the kernel's critical sections): Preempt-RT
  • Discussion about uKernels vs coKernels
  • Simple example of coKernel system (Xenomai)
• Fourth lesson: 2021/04/27, 9:30 -> 12:00 (videos of the first part and second part of the lesson, in italian)
  • Using uKernels in practice: example with l4re
  • About uKernels, coKernels, nanoKernels and... Hypervisors
  • Some more details about uKernel-based systems (capability systems, etc...)
• Fifth lesson: 2021/05/04, 9:30 -> 12:00 (videos of the first part and second part of the lesson, in italian)
  • From nanoKernels to hypervisors
  • Recalling some basic concepts about virtualization
  • Bare-metal hypervisors vs Hosted hypervisors
  • About Xen, paravirtualization and similar amenities
  • Trap & Emulate: basic example
• Sixth lesson: 2021/05/11, 9:30 -> 12:00 (videos of the first part and second part of the lesson, in italian)
  • Loading and parsing kernels in bare-metal hypervisors
  • Discussion about bare-metal vs hosted hypervisors, again
  • Example of hosted hypervisor (based on Intel VT-x)
• Seventh lesson: 2021/05/18, 9:30 -> 12:00 (videos of the first part and second part of the lesson, in italian)
  • Hosted hypervisors and Intel VT-x, again: some experiments with the example
  • Hypervisors and Virtual Machine Monitors: KVM and QEMU
    • Some simple examples about using KVM
    • Handling I/O in KVM-based VMs
  • Some discussion about real-time virtualization
• Eighth lesson: 2021/06/01, 9:30 -> 12:00 (videos of the first part and second part of the lesson, in italian)

Project Ideas

Here are some ideas for possible projects for the exam. Remember to contact me when you chose one.

Slides and References:

• Introduction to the course
• Something about Real-Time OSs
• Quick summary about OS kernels
• More about the OS kernel latency
• Kernel architectures for reducing the latency
• uKernels vs Dual Kernels
• List of references to scientific papers about the arguments described in the course
• About periodic tasks
• About domains, hypervisors and similar amenities
• Something more about uKernels
  • A scientific paper comparing uKernels and hypervisors...
  • ...And a response to it
  • Someone even invented microvisors!
• Some background on CPU virtualization and hardware support for advanced CPU virtualization
• Hypervisors and real-time

Examples:

• Examples about periodic timers
• Some tests with Xenomai
• Example about using l4re. Follow these instructions to use it.
• Very simple example about trap and emulate, also showing an issue with the x86 ISA not respecting Popek & Goldberg requirements (the instruction to read the "Machine Status Word" register is sensitive but not privileged)
  • Same example, with the guest code separated in a different executable file (as a reference, see how GRUB loads Xen and its Dom0 kernel or how l4re loads its servers)
  • Same example again, this time parsing the ELF format of the guest to load it. Notice how this bare-metal hypervisor has to implement memory management and other functionalities needed by the ELF parser
• Simple example about Intel VT-x, using a hosted hypervisor
• Example with KVM
  • Small improvement of the KVM example, separating the guest code in a different executable
  • Patch showing how to handle I/O

Useful Links:

• The Linux kernel
• The Preempt-RT patchset
  • Notes about developing real-time applications
• Dual-kernel systems: Xenomai, EVL, RTAI
• Microkernels: l4re, sel4, Genode, GNU Hurd (based on Mach), Google Zircon (note: "handles" are similar to capabilities), ...
• Hypervisors: Xen, ACRN, Jailhouse, ...
• Some standards about executable formats (useful to implement a loader / ELF parser in a hypervisor or microkernel)
• Some lightweight VMs / VMMs using KVM (see also QEMU's microvm): the Intel cloud hypervisor, Amazon's FireCracker, ...
  • To see a reference simple VMM based on KVM, check TinyEMU or kvmtool
• The Rump Kernels, useful for example to build unikernels based on openbsd source code. Notice that the rumpkernel.org site seems to be down